It is well known that extremely dangerous conditions can arise when a vehicle, in particular a transport vehicle which may be heavily loaded, has one or more under-inflated tires. This can lead to overheating of the tires with subsequent blow-outs and the possibility of accidents. Also, in the case of double wheels, it may lead to one tire becoming substantially flat and the sidewalls of the two tires rubbing against each other thereby destroying both tires. Irrespective of this dangerous situation, the cost of the tires alone is substantial.
Numerous different attempts have been made at providing tire pressure monitoring and indicating devices, generally for permanent or long term association with pneumatic tires, or a vehicle fitted with such tires, for the purpose of enabling under-inflated tires to be easily and swiftly detected.
Many of the prior proposals have involved rather complicated electronic arrangements in which information as to whether or not a tire is under-inflated is conveyed from a wheel, by electromagnetic radiation or magnetic fields, to a receiver on the body, the receiver being coupled to a control unit for informing a driver of the situation. While some of these devices have indeed operated effectively, they are not favoured, and suffer from various disadvantages in different localities.
It is applicant's belief that the problem can be substantially alleviated simply by checking the tires of a vehicle before embarking on a journey as, for the most part, an under-pressure tire will generally be capable of detection at that stage.
It is, however, unlikely that a driver of a vehicle will be in possession of a pocket pressure gauge to check the tires. Also, the removal and replacement of the valve caps is tedious.
It is, accordingly, the object of this invention to provide a tire pressure indicator of simple construction which can be in long term association with a tire valve, and whereby the manual checking whether or not the associated tire is under-inflated is rendered extremely simple.